The present invention relates to a process for producing glass noodles using genetically modified starch, a glass noodle which has been produced using genetically modified starch, and to the use of genetically modified starch for producing glass noodles and demoldable gels.
The essential features of the glass noodles of the invention are characterizable by physicochemical properties such as water absorption capacity, transparency, cooking loss and elasticity and thus define the appearance, cooking behavior and the texture (bite firmness, etc.) of the noodle.
To produce glass noodles, conventionally a paste is first prepared from mung bean starch and water, from which paste by further addition of starch a dough is prepared which can then be extruded, for example through fine nozzles into boiling water. After a short cooking time the noodles are cooled, resp., quenched and then dried.
The use of mung bean starch alone in the production of noodles leads to a very high quality glass noodle which, when dried, is white, appears transparent after boiling or cooking, has a low water absorption capacity and a high tensile strength and high elasticity. Since mung bean starch is produced in a highly complex production process, it is comparatively expensive. There have therefore been many attempts to replace mung bean starch in whole or in part by more inexpensive, occasionally chemically modified starches from wheat, potatoes, tapioca, sago, cassava, corn etc. (Kim et al., 1996, Cereal Chem. 73(3), 302-308, Kasemsuwan and Jane, 1995, AACC Annual Meetings, Abstract No. 185, Kasemsuwan et al. 1998, Carbohydrate Polymers 32, 301-312, Chang, 1983, Proceedings of the 6th Int. Congress of Food Sci. And Techn., 1, 111-112, Collado and Corke, 1997, Cereal Chem. 74(2), 182-187).
However, replacing the mung bean starch by more inexpensive starches in the doughmaking is accompanied by various disadvantages which primarily lead to a considerably reduced quality, i.e. reduced elasticity and a higher water absorption capacity (softer consistency) of the noodle.
The object of the present invention is therefore to provide an alternative production of glass noodles of high quality with good economic efficiency.
A further object of the invention is to provide an alternative to the limited availability of mung bean starch, especially for glass noodle production. In addition, the object of the invention is to provide an alternative for the use of optionally chemically modified starches of various origin in the production of glass noodles, in order to reduce production times and production costs.
These and other objects are achieved effectively by the present invention, as follows from the description below and the examples set forth.
Modern methods of gentechnology make available a multiplicity of transgenic, starch-producing plants, in particular corn, potato, wheat or rice, from which starch, that is to say within the meaning of the present invention xe2x80x9cgenetically modified starchxe2x80x9d can be isolated, which starch sometimes has considerably modified physicochemical properties, for example a change in the amylose/amylopectin ratio, the chain length distribution of the amylopectin, the degree of phosphorylation and the mineral content (Ca2+, Mg2+, etc.) or the lipid content, etc.
Owing to the modified properties of said genetically modified starches some completely novel and also highly surprising possibilities for use are created given the extremely wide use of starches in industry and in the food sector.
It has now been found that, surprisingly, starches from genetically modified plants (GMS), preferably from tapioca, corn, wheat and/or potatoes, in particular, from wheat and/or potatoes and very particularly from potatoes, having an amylose content of greater than 25%, preferably  greater than 30, in particular  greater than 33% (amylose content determined by the method of Hovenkamp-Hermelink et al., 1988, Potato Research 31: 241-246) and a gel strength of about 90-160 g, preferably 100-160 g, in particular 110-160 g (gel strength determined in accordance with Example 3 B) are outstandingly suitable for producing glass noodles or demoldable gels.
The present invention therefore relates to a process for producing glass noodles in which starch, especially starch from tapioca, potatoes, corn and/or wheat, preferably potatoes and/or wheat, in particular potatoes, having an amylose content of at least 25%, preferably  greater than 30%, in particular  greater than 33% and a gel strength of about 90-160 g, preferably 100-160 g, in particular 110-160 g, is substituted and in processed in a conventional manner to give a glass noodle, in which preferably at least 30%, particularly preferably about 30-90%, in particular about 35-80%, and very particularly about 40-65% of the conventionally used mung bean starch is replaced by said starch.
In the process of the invention for glass noodles preference is furthermore given to starches from tapioca, potatoes, corn and/or wheat which have a phosphate content of at least 0.5 nmol, preferably 1 nmol and in particular 1.5 nmol of glucose-6-phosphate (G6P)/mg of starch (determined by the enzymatic method described in Example 8b of the international patent application WO 97/11188 A1).
The invention finally further relates to a glass noodle which features an elasticity of at least 1.5 g/cm, preferably at least 1.7 g/cm and/or a water absorption capacity of a maximum of 550%, preferably a maximum of 530%, in particular a maximum of 500%, at a diameter from about 0.4 to 0.45 mm of the dried noodle, obtainable by the process according to the invention for producing glass noodles, in which starch from tapioca, potatoes, corn and/or wheat, preferably potatoes and/or wheat, in particular potatoes, having an amylose content of at least 25%, preferably  greater than 30%, in particular  greater than 33%, and a gel strength of about 90-160 g, preferably 100-160 g, in particular 110-160 g, is processed in a conventional manner to give a glass noodle, in which preferably at least 30%, in particular about 30-90%, particular preferably about 35-80%, and very particular preferably about 40-45%, of the conventionally used mung bean starch is replaced by said starch and said starch in a further preferred embodiment has a phosphate content of at least 0.5 nmol, preferably 1 nmol, and in particular 1.5 nmol of G6P/mg of starch.
The invention also relates to the use of starch, especially a starch from tapioca, potatoes, corn and/or wheat, preferably potatoes and/or wheat, in particular potatoes, having an amylose content of at least 25%, preferably  greater than 30% in particular  greater than 33% and a gel strength of about 90-160 g, preferably 100-160 g, in particular 110-160, and a phosphate content of at least 0.5 nmol, preferably 1 nmol, and in particular 1.5 nmol of G6P/mg of starch in a process for producing glass noodles or demoldable gels.
Inasmuch as the use of said starches relates to the production of demoldable gels, for their production, preferably, an about 2-15% strength boiled suspension of said starch is cooled to a temperature of 0-30xc2x0 C., preferably room temperature (i.e. about 15-25xc2x0 C.). The present invention also relates to a process for producing demoldable gels in which starch, especially a starch from tapioca, potatoes, corn and/or wheat, preferably potatoes and/or wheat, in particular potatoes, having an amylose content of at least 25%, preferably  greater than 30% in particular  greater than 33% and gel strength of about 90-160 g, preferably 100-160 g, in particular 110-160 g, and a phosphate content of at least 0.5 nmol, preferably 1 nmol, and in particular 1.5 nmol of G6P/mg of starch, in an about 2-15% strength suspension, preferably 3-12% strength, in particular 4-10% strength suspension, is boiled and cooled to a temperature of about 0-30xc2x0 C., preferably about 15-25xc2x0 C.
The term xe2x80x9cgenetically modified starchesxe2x80x9d (GMSs) for the purposes of the present invention means starches from genetically modified plants, preferably from tapioca, corn, wheat and/or potatoes, in particular from wheat and/or potatoes, especially from potatoes, which have been modified by biotechnological methods, preferably with respect to their side-chain distribution (e.g., their amylose content), their phosphate content and/or their gel formation properties, which can be characterized, for example, by means of the ration of final viscosity to peak viscosity in an RVA profile (cf. Example 3 A) of their gel strength (cf. Example 3 B). GMSs are disclosed, for example, by the patent applications or patent hereinafter, the listing hereinafter not being complete:
WO 90/12876A1 (U.S. Pat. Nos. 6,147,277, 5,789,657, and 5,498,832), WO 91/19806A1, WO 92/11375A1 (U.S. Pat. No. 5,856,467), WO 92/11376A1 (U.S. Pat. No. 5,824,798), WO 92/11382A1 (U.S. Pat. No. 5,349,123), WO 92/14827A1 (U.S. Pat. No. 6,215,042), WO 94/09144A1, WO 94/11520A1, WO 95/04826A1 (U.S. Pat. Nos. 6,001,628, and 4,694,879), WO 95/07355A1 (U.S. Pat. No. 6,066,782), WO 95/26407A1 (U.S. Pat. No. 6,103,893), WO 95/34660A1 (U.S. Pat. No. 6,096,945), WO 95/35026A1 (U.S. Pat. Nos. 6,218,155, 5,824,790, and 5,576,048), WO 96/15248A1 (U.S. Pat. No. 6,130,367), WO 96/19581A1 (U.S. Pat. No. 6,117,665), WO 96/27674A1 (U.S. Pat. No. 6,162,966), WO 96/34968A1, WO 97/04112A1 (U.S. Pat. No. 6,147,279), WO 97/04113A1 (U.S. Pat. No. 6,232,122), WO 97/11188A1 (U.S. Pat. No. 6,207,880), WO 97/16554A1, WO 97/20040A1 (U.S. Pat. No. 6,169,226), WO 97/22703A1, WO 97/45545A1, WO 98/11181A1, WO 98/11228A1, WO 98/15621A1 (U.S. Pat. Nos. 6,143,963, and 4,865,451), WO 98/37213A1, WO 98/37214A1, CA 2,061,443, DE 19820607.0, P1 19820608.9, DE 19836097.5, DE 19836098.3, DE 19836099.1, EP-A-0521621 (U.S. Pat. Nos. 5,830,724, and 5,365,016), EP-A-0703314, EP-A-0737777, EP-A-0779363 or U.S. Pat. No. 5,300,145. WO 97/11188A1 extensively describes the GMSs used in the examples hereinafter; the contents of WO 97/11188A1 (and its U.S. equivalent, U.S. Pat. No. 6,207,880) are hereby explicitly incorporated by reference.
In the production of glass noodles, the use according to the invention of GMSs in the process of the invention allows at least 30% of the conventionally required mung bean starch to be replaced, preferably about 30-90%, particularly preferably about 35-80%, and in particular about 40-45% without any significant loss in quality of the glass noodles occurring.
Another preferred embodiment of the process of the invention additionally comprises the steps of
a) preparing a paste using mung bean starch and
b) preparing a noodle dough using said GMS.
For the purposes of the present invention, xe2x80x9cglass noodlexe2x80x9d means any noodle which has an elasticity (tensile strength/elongation) of at least 1.5 g/cm, preferably at least 1.7 g/cm, and/or a water absorption capacity of a maximum of 550% (w/w), preferably a maximum of 530%, particularly preferably a maximum of 500%, determined at a noodle diameter of about 0.4-0.45 mm. However, the term xe2x80x9cglass noodlexe2x80x9d is not limited to a noodle of a diameter of about 0.4-0.45 mm, but applies to each noodle of the same composition.
For the purposes of the present invention, xe2x80x9celasticityxe2x80x9d is defined as the tensile strength/elongation of the cooked noodle and is determined by tensile tests using a texture analyzer (Texture Analyser TA-XT2, Stable Micro Systems, UK). For this purpose, individual glass noodles (diameter 0.4-0.45 mm) after boiling (100 s at 100xc2x0 C.) and cooling (60 s at 20xc2x0 C.) were wound round an upper and lower round holder of the instrument, so that the intermediate space was 50 mm. The noodles were then extended at 1 mm/s up to break point and a stress-strain diagram was recorded. From the maximum required force to break a noodle and the elongation of the noodle at the time point of break, the ratio force/distance in g/cm was calculated as a measure of the elasticity.
The xe2x80x9ccooking lossxe2x80x9d was reported as dry residue of the cooking water based on the initial noodle dough mass, and the xe2x80x9ctransparencyxe2x80x9d was determined by optical evaluation.
xe2x80x9cWater absorption capacityxe2x80x9d for the purposes of the description is defined as the amount of water in g which was taken up by the noodle during the cooking process (100 s at 100xc2x0 C.), based on the initial noodle dough mass.